The police also confiscated computers and phones from his home in Beijing, said US-based organisation Human Rights Watch in China.

Xu was arrested in 2009 on tax evasion charges which were eventually dropped after public outcry.

His lawyer, Wang Weiguo, questioned the allegations against Xu, who was placed under house arrest in April due to his campaign to push for greater asset disclosure of government officials.

“How can a man who has been held under house arrest disrupt public order?” Wang told the South China Morning Post.

According to Wang, Xu headed the New Citizen’s Movement, a group campaigning against government corruption, and said he “never advocated violence in his writings”.

Several members of the group have been arrested in recent months.

Zu’s arrest is the latest in a crackdown on political dissent even as President Xi Jinping pledged to root out corruption.

“While the government is willing to show its efforts on corruption by detaining and prosecuting a few high-profile cases, it’s not really very serious on systematically stamping out corruption,” said Maya Wang, Asia researcher at Human Rights Watch in Hong Kong.